Polarization effects in non-relativistic epep scattering

The cross section which addresses the spin-flip transitions of a proton (antiproton) interacting with a polarized non-relativistic electron or positron is calculated analytically. In the case of attraction, this cross section is greatly enhanced for sufficiently small relative velocities as compared to the result obtained in the Born approximation. However, it is still very small, so that the beam polarization time turns out to be enormously large for the parameters of $e^{\pm}$ beams available now. This practically rules out a use of such beams to polarize stored antiprotons or protons.Comment: 9 pages; version accepted for publication in Nucl.Instr.Methods B where cross sections without averaging over directions of relative velocities are adde

Spin-dependent part of ppˉp\bar{p} interaction cross section and Nijmegen potential

Low energy $p\bar{p}$ interaction is considered taking into account the polarization of both particles. The corresponding cross sections are calculated using the Nijmegen nucleon-antinucleon optical potential. Then they are applied to the analysis of the polarization buildup which is due to the interaction of stored antiprotons with polarized protons of a hydrogen target. It is shown that, at realistic parameters of a storage ring and a target, the filtering mechanism may provide a noticeable polarization in a time comparable with the beam lifetime.Comment: 10 pages, 3 figure

High-energy expansion of Coulomb corrections to the e+e- photoproduction cross section

First correction to the high-energy asymptotics of the total $e^+e^-$ photoproduction cross section in the electric field of a heavy atom is derived with the exact account of this field. The consideration is based on the use of the quasiclassical electron Green function in an external electric field. The next-to-leading correction to the cross section is discussed. The influence of screening on the Coulomb corrections is examined in the leading approximation. It turns out that the high-energy asymptotics of the corresponding correction is independent of the photon energy. In the region where both produced particles are relativistic, the corrections to the high-energy asymptotics of the electron (positron) spectrum are derived. Our results for the total cross section are in good agreement with experimental data for photon energies down to a few $MeV$. In addition, the corrections to the bremsstrahlung spectrum are obtained from the corresponding results for pair production.Comment: 22 pages, 7 figures, RevTeX.Typos are corrected. The numerical results, figures and conclusions remain unchanged as they were obtained using correct formula

Finite nuclear size effect on Lamb shift of s1/2, p1/2, and p3/2 atomic states

We consider one-loop self-energy and vacuum polarization radiative corrections to the shift of atomic energy level due to finite nuclear size. Analytic expressions for vacuum polarization corrections are derived. For the self-energy of p1/2 and p3/2 states in addition to already known terms we derive next-to-leading nonlogarithmic Z\alpha-terms. Together with contributions obtained earlier the terms derived in the present work give explicit analytic expressions for s1/2 and p1/2 corrections which agree with results of previous numerical calculations up to Z=100 (Z is the nuclear charge number). We also show that the finite nuclear size radiative correction for a p3/2 state is not small compared to the similar correction for a p1/2 state at least for small Z.Comment: 12 pages, 7 figure

Spin effects in ppˉp\bar p interaction and their possible use to polarize antiproton beams

Low energy $p\bar p$ interaction is considered taking into account the polarization of both particles. The corresponding cross sections are calculated using the Paris nucleon-antinucleon optical potential. Then they are applied to the analysis of the polarization buildup which is due to the interaction of stored antiprotons with polarized protons of a hydrogen target. It is shown that, at realistic parameters of a storage ring and a target, the filtering mechanism provides a noticeable polarization in a time comparable with the beam lifetime.Comment: 10 pages, 4 figure

Relativistic Oscillator Model and Delbr\"uck scattering

Elastic scattering of photons in a Lorentz-scalar potential via virtual spin-zero particle-antiparticle pairs (`` Delbr\"uck scattering") is considered. An analytic expression for the Delbr\"uck amplitude is found exactly in case of an oscillator potential. General properties of the amplitude and its asymptotics are discussed.Comment: 8 pages, LATEX, BINP 94-6

Nuclear Structure Corrections to Deuterium Hyperfine Structure and Lamb Shift

The low-energy theorem for the forward Compton scattering is generalized to the case of an arbitrary target spin. The generalization is used to calculate the corresponding contribution to the deuterium hyperfine structure. The nuclear-structure corrections are quite essential in this case due to the deuteron large size. Corrections of this type calculated here remove the discrepancy between the theoretical and experimental values of the deuterium hyperfine splitting. Explicit analytical result is obtained also for the deuteron polarizability contribution to the Lamb shift.Comment: 14 pages, latex, no figure

Finite nuclear size and Lamb shift of p-wave atomic states

We consider corrections to the Lamb shift of p-wave atomic states due to the finite nuclear size (FNS). In other words, these are radiative corrections to the atomic isotop shift related to FNS. It is shown that the structure of the corrections is qualitatively different from that for s-wave states. The perturbation theory expansion for the relative correction for a $p_{1/2}$-state starts from $\alpha\ln(1/Z\alpha)$-term, while for $s_{1/2}$-states it starts from $Z\alpha^2$ term. Here $\alpha$ is the fine structure constant and $Z$ is the nuclear charge. In the present work we calculate the $\alpha$-terms for $2p$-states, the result for $2p_{1/2}$-state reads $(8\alpha/9\pi)[\ln(1/(Z\alpha)^2)+0.710]$. Even more interesting are $p_{3/2}$-states. In this case the ``correction'' is by several orders of magnitude larger than the ``leading'' FNS shift.Comment: 4 pages, 2 figure

Studies of New Vector Resonances at the CLIC Multi-TeV e+e- Collider

Several models predict the existence of new vector resonances in the multi-TeV region, which can be produced in high energy e+e- collisions in the s-channel. In this paper we review the existing limits on the masses of these resonances from LEP/SLC and TEVATRON data and from atomic parity violation in some specific models. We study the potential of a multi-TeV e+e- collider, such as CLIC, for the determination of their properties and nature.Comment: 17 pages, 16 EPS figures, uses JHEP3.cl

Electric polarizabilities of proton and neutron and the relativistic center-of-mass coordinate

We argue that the relativistic correction $\delta{\bf R}_{c.m.}$ to the center-of-mass vector can lead to the approximate equality of the proton and neutron electric polarizabilities in the quark model. The explicit form of $\delta{\bf R}_{c.m.}$ depends only on the non-relativistic potential between quarks. In particular, this correction is the same for the potential generated by Lorentz-vector and -scalar interactions.Comment: 8 pages, LaTeX, conclusion extende